Now I’m checking from the REST API. His userid is: 476889899 (I will call him as my user)
When I request from REST API;
GET/1.1/friends/ids, then I get 4453 friends
GET/1.1/followers/ids, then I get 6150 followers
1 friend and 2 followers missing.

Then I compare friends and followers: array_diff($all_friends_ids, $all_followers_ids)
I check for his friends that doesn’t follow him.
Result is 2 people. Userids are => 257648899 and 1356883932
These two people doesn’t follow my user, but my user follows them.

Then I check for friendship:
GET/1.1/friendships/show/ source: 476889899 target: 257648899
Result is: 200 both of them follows.
But 257648899 doesn’t appear in the followers list of my user.

It seems like 476889899’s followers list is missing for the user 257648899.
So my charts becomes wrong because of these type of error.
REST API gives absent data and this makes my charts unreliable to my visitors.
What can be the cause of this API behaviour ?